1. Field of the Invention
The present invention relates to a system and method for providing simulated hardware-in-the-loop testing of a wireless communications network. More particularly, the present invention relates to a system and method which employs an optical matrix-vector multiplier for performing optical signal processing to simulate radio frequency (RF) signal propagation characteristics in a mobile wireless communications network.
2. Description of the Related Art
In recent years, a type of mobile communications network known as an “ad-hoc” network has been developed for use by the military. In this type of network, each user terminal is capable of operating as a base station or router for the other user terminals, thus eliminating the need for a fixed infrastructure of base stations. Details of an ad-hoc network are set forth in U.S. Pat. No. 5,943,322 to Mayor, the entire content of which is incorporated herein by reference.
More sophisticated ad-hoc networks are also being developed which, in addition to enabling user terminals to communicate with each other as in a conventional ad-hoc network, provide intelligent access points (IAPs) that enable the user terminals to access a fixed network and thus communicate with other user terminals, such as those on the public switched telephone network (PSTN), and on other networks such as the Internet. Details of these types of ad-hoc networks are described in U.S. patent application Ser. No. 09/897,790 entitled “Ad Hoc Peer-to-Peer Mobile Radio Access System Interfaced to the PSTN and Cellular Networks”, filed on Jun. 29, 2001, and in U.S. patent application Ser. No. 09/815,157 entitled “Time Division Protocol for an Ad-Hoc, Peer-to-Peer Radio Network Having Coordinating Channel Access to Shared Parallel Data Channels with Separate Reservation Channel”, filed on Mar. 22, 2001, the entire content of both of said patent applications being incorporated herein by reference.
To test a wireless network, such as an ad-hoc wireless network as described above, with modem radio hardware-in-the-loop, it is desirable to provide a testbed that would simulate a deployed network of transceivers in an automated and repeatable fashion. The design and deployment of many kinds of communication networks including cellular, cable, satellite, ad-hoc, and others can benefit from a test capability of this kind. Also, the specific ability to exercise a network of modem or radio transceivers in the presence of a controlled and scripted RF simulation environment would be invaluable.
A conventional method of incorporating RF signal propagation effects and transceiver mobility into the testing of a network has typically involved the use of a small group of test personnel with mobile transceivers. In the case of point-to-point networks, RF switching matrices have been employed without the need for full fanout of the network nodes. However, for systems of greater connectivity, it is usually necessary to exclude the physical layer from network test.
An example of a system having this greater connectivity is an ad-hoc wireless network of the type discussed above. The ad-hoc wireless network comprises a plurality of combined router/IAP devices and subscriber radios, such as mobile user terminals, that are fully connected in the RF sense with a dynamic link attenuation for each path between radios that is under real-time control. Such attenuation models propagation path loss, fading, mobility-induced power changes, and the implementation of power control algorithms which govern adjustment of individual transmitter power levels. A brute force approach to simulating this scenario would involve connecting a population of radios together using a full fan out microwave switching matrix with digitally-controlled attenuation along each path. However, this is generally considered to be a prohibitively expensive technique, the cost of which would be further exacerbated by providing real-time control of path delay.
Accordingly, a need exists for a system and method capable of performing simulation testing on a communications network, such as an ad-hoc communications network, with minimal complexity and cost.